There is known a barge-in function as a technique to perform a correct speech recognition. While a guidance speech such as “please speak at the tone” is outputted, a user may utter a recognition speech such as “drive home.” Even in such a case, the barge-in function performs a correct speech recognition of the recognition speech. In detail, a guidance speech inputted into a speaker at the same time when a user utters a recognition speech is removed; the recognition rate of recognition speech-data is prevented from decreasing. A conventional configuration achieving a barge-in function includes an additional microphone in addition to a microphone for input of recognition speech uttered by a user. This configuration uses a guidance speech inputted into the additional microphone as a reference speech that removes a guidance speech inputted into the microphone for input of recognition speech (for example, refer to Patent literatures 1 and 2).